3D printed Pringles Can "Rear Eject Bomb Rocket MK II" Build Thread (3D printed "Kit" build)

Shop deals on ebay
eggtimer rocketry
SilicdyneTRF
The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Aslansmonkey said:
Hey Ken, when's the launch? Waiting on updates here.
Click to expand...
Hey there! Sorry, launch was this past Saturday and I wasn't able to finish the build. I really wanted to and tried, but in the end realized I wouldn't be able to and had to get other rockets prepped (I was up past 3AM and had to get up at 7AM). Personal life got in the way too...it's been likely the craziest past few weeks I've ever had! Still, I'm anxious to continue this and plan to next week (currently my wife has me helping her on her work since she has a monster project...she's been working almost non-stop and sometimes through the night and so pretty much every spare moment I have aside from what was pre-planned/booked is taken for now).

So unfortunately duty before fun...no matter how awesome. ;)
 
That tube contains 4 regular Pringles cans. I have one sitting next to me that some friends of mine picked up for me. It's being made into a 29mm AAMRAM style rocket. I'm using 3mm plywood centering rings and sub fins going to the motor tube under 3D printed parts for it. I'm sure I'll post the designs to Thingiverse when I'm done, but that's a longer term winter project so I'm not really rushing it. The design I post will likely include 3D printable centering rings as well, but if someone uses those they should print them in ABS rather than PLA for the additional temp protection.

Note I am NOT a tripoli member, so I won't be launching mine with anything larger than a G-80, but the motor tube is 29mms by 430mm and I think that's long enough to take 6 grain Cesseroni's. I simply don't fly enough to warrant the certification costs for high power and I'm more interested in the designing than actual flying. I mean, they HAVE to fly at least once or the design is a failure, but this rocket doesn't need to fly on anything more than a G to prove itself to me.

As you can see in the photo, I've only the tail cone and motor tube assembly done so far. The ring on the body tube is a guide for cutting the fin slots and can also be used to hold those fins perpendicular to the motor/body tube while the glue is drying. I have it place approximately where I intend to cut the body tube to make a payload section, which cuts down on the volume of body tube the ejection charge has to work with and provides an avionics bay for anyone wanting to use it for that. The canard fins will be about where that ring is.

Note this tube is probably fine for a G powered motor. It might be a little fragile for anything over that, I'm not really sure. If you plan to build a true high power rocket from one of these tubes you might consider glassing it.
 

Attachments

  • 20211109_080006.jpg
    20211109_080006.jpg
    48.6 KB · Views: 8
Continuing on, I lined up the parts and started to glue on the upper rod guide. Since I was likely keeping this unpainted ("Purple Prangles" lol), I wanted it placed so it wouldn't block the images up front and not too low to keep it looking bomb-like. I also chose to align it with a line that runs down the side of the graphics for easier placement of the lower guide. I then used CA for less mess vs. epoxy.IMG_20220622_225232315.jpg
 
Tube time! I mixed up some epoxy to glue the main bt into the rocket. (Note: I used a stock length bt, but it would probably have been easier to cut it to size first). Be aware of the earlier kevlar line...there are a few ways to keep it out of the way (pull through the tube, pull out from the top, curl and wrap, etc.). I also epoxied the lower tail cone at the same time to ensure proper alignment.

IMG_20220622_225818058.jpgIMG_20220622_231437600.jpg
 
Last edited:
The center ring separates the main chute from the pod chute. The instructions noted it's "for the middle of the motor pod", but I placed it closer to the motor end since the pod chute is smaller than the main chute. Also it was noted that there is a nub on there to mount a screw eye and the nub should point down, however I just drilled it through and for a knotted kevlar line and epoxied the knot. I also pointed the nub up (didn't seem any big deal to me at the time).
IMG_20220623_231105213.jpg

Don't forget a motor block ring! I couldn't find my stash, so I cut the end off a used D motor. I also glued it in far enough for an E/F motor.

IMG_20220623_005638500.jpg
 
So what would a build be without some doofing drama? I made the mistake of using a new E9 motor to space the motor block ring and it ended up glued to the motor pod due to an errant glue drip I didn't see. 🤦‍♂️

So after destroying both the pod tube AND possibly compromising the E9 motor trying to salvage it, I just ripped up the tubing and redid the motor pod (see wreckage on the left).
IMG_20220624_144132391.jpg
 
The instructions note that a 9" chute was used for the pod and a 15" chute for the main rocket. I had a 9" on hand and for the rocket I used a JonRocket chute (I have a bunch that were included free in my past orders) and decided to try cutting it a bit differently by scalloping the edges, adding a spillhole and then taping. cross through the spillhole after deciding the hole was too big.
IMG_20220624_224322254.jpg
IMG_20220624_225157934.jpg
IMG_20220625_103555343.jpg
 
You're supposed to test fit the pod into the main tube and check that it's not loose nor binding. The forward most ring was a bit loose, so I just added a bit of masking tape around the ring. I then added a D12-3 motor (with the spacer taped on so it's easier to remove) and added some dog barf to absorb the ejection gasses.
IMG_20220625_131613571.jpg
IMG_20220625_131413519.jpg
 
Last edited:
Time to wrap things up, so I connected the main chute to the main kevlar line, wrapped that chute around the upper pod, inserted it into the rocket, then wrapped the pod chute around the pod and inserted into the rocket. the pod fit was a bit loose, so I added tape to the pod end.
IMG_20220625_132108744.jpg
 
Upon further inspection (which definitely helps when launching rockets!), I decided that the launch lugs were too far apart, so I added a third lug that I had as an extra print when one of two came out a bit wonky (they're easy prints so I was doing them in pairs).

In this case, I cut the lug ring so it can be fit over the finished can, which is not a problem since I'll be gluing the entire ring to the can anyway.

I found a nice spot near the middle and used a large rod to ensure alignment and glued on.

IMG_20220625_184510835.jpg
 
It looks like you have the cords wrapped around the tube for that upper chute (the bomb one). If so, don't do that, it'll tangle on the pod on ejection. The chute and it's associated strings for the bomb portion need to be stuffed loosely in the body tube. The pod should pull them out, but not get in their way.

I use a BBQ Skewer or more often a spare launch rod to gently stuff them in.

The pod chute can wrap around the tube more as it'll just roll off. I originally used a streamer on the pod but it falls a little fast that way.

Be sure to warn people at the launch that it's a two part recovery rocket. It'll help forestall the inevitable "is it supposed to come apart like that?" questions (which you will get anyway).


Post a video of the launch, if you get the chance. I'd love to see it.
 
Aslansmonkey said:
It looks like you have the cords wrapped around the tube for that upper chute (the bomb one). If so, don't do that, it'll tangle on the pod on ejection. The chute and it's associated strings for the bomb portion need to be stuffed loosely in the body tube. The pod should pull them out, but not get in their way.

I use a BBQ Skewer or more often a spare launch rod to gently stuff them in.

The pod chute can wrap around the tube more as it'll just roll off. I originally used a streamer on the pod but it falls a little fast that way.

Be sure to warn people at the launch that it's a two part recovery rocket. It'll help forestall the inevitable "is it supposed to come apart like that?" questions (which you will get anyway).


Post a video of the launch, if you get the chance. I'd love to see it.
Click to expand...
Great advice! For my old R2D2 pod I used to wind it without issue, but in this case I can see how it can snag... especially given I've added some masking tape to the forward pod ring.

Regarding telling the RSO/announcer, also a good idea and I'm already in the habit of listing down any special notes... I often launch fairly unusual stuff, so they know me by now. Recently I launched the Estes MIRV, which is a 2-stage, 4-motor, with recovery as 4 separate parts tumble and break apart. 🙂

Side note is that I most likely can't make the club's Saturday launch and the weekend is currently forecasting rain, so there is a chance of postponing.
 
Hi Everyone! I was able to launch this rocket at yesterday's Metra NY Club (on an E12-4 after realizing that's what the designer used) and I hope it was worth the wait! 😁👍
IMG_20220703_104450681_HDR.jpg

This was marked heads up by the RSO (ya think it was because I named it "Mr. Prangles"?😆), however the boost was laser straight (it sounded amazing to me) and I heard others remark at how it was a great flight!

The pod popped out right at apogee and both chutes deployed. The main opened, however two points stuck together (very slightly singed?) and this caused the rocket to twirl/rock on it's way down.
IMG_20220703_114102767_HDR.jpg
IMG_20220703_114114833_HDR.jpg
IMG_20220703_114338739_HDR.jpg
Was still a great and successful launch and it exceeded my expectations. I absolutely love how it flies on E12-4!
 

Similar threads

J
3D Printing New to 3D printing
Replies
12
Views
710
RocketMan3D
R
BigMacDaddy
F-18 Super Hornet (3D Printed Parts + Plywood Wings/Fins + BT-60/BT-55 tubes)
Replies
11
Views
360
cwbullet
cwbullet
Dave A
3D Printing Newbie here to 3D Printing.
Replies
4
Views
546
cwbullet
cwbullet
T
Stubby Midpower with Rear Ejection - Stinger!
Replies
13
Views
1K
thzero
T
Ray Lecture
Upscale Estes Venus Probe Build Thread
Replies
24
Views
951
Blast it Tom!
Blast it Tom!

Latest posts

Back
Top